Thisvolumecontainspapersselectedforpresentationatthe2004AnnualConf- enceoftheEuropeanAssociationforComputerScienceLogic,heldonSeptember 20–24, 2004 in Karpacz, Poland. The CSL conference series started as the International Workshops on C- puterScienceLogic,andthen,after?vemeetings,becametheAnnualConference of the European Association for Computer Science Logic. This conference was the 18th meeting, and the 13th EACSL conference. Altogether 99 abstracts were submitted, followed by 88 papers. Each of these paperswasrefereedbyatleastthreereviewers.Then,afteratwo-weekelectronic discussion, the Programme Committee selected 33 papers for presentation at the conference. Apart from the contributed papers, the Committee invited lectures from Albert Atserias, Martin Hyland, Dale Miller, Ken McMillan and Pawel Urzyczyn. WewouldliketothankallPCmembersandthesubrefereesfortheirexcellent work. The electronic PC meeting would not be possible without good software support. We decided to use the GNU CyberChair system, created by Richard van de Stadt, and we are happy with this decision. We also would like to thank Micha l Moskal who installed and ran CyberChair for us. Finally, we would like to thank ToMasz Wierzbicki, who helped with the preparation of this volume. We gratefully acknowledge ?nancial support for the conference received from the Polish Committee for Scienti?c Research, and Wroc law University. July 2004 Jerzy Marcinkowski and Andrzej Tarlecki Organization CSL 2004 was organized by the Institute of Computer Science, Wrocla w University.